From U.S. Pat. No. 6,091,404 a trackball module is known, which comprises a trackball for being manipulated by hand and a sensor device for detecting a turning of the trackball arranged under the trackball. The trackball and the sensor device are received by a support device, which can be inserted into a portable computer and detached from the portable computer.
It is a disadvantage of such kind of a trackball module that the trackball module comprises a large height leading to a corresponding large height of an electrical device that uses such a kind of trackball module, such as a portable computer.